This invention is concerned with the storage and transmittal of fluid to a heat transfer station. The transmitted fluid coacts with the heat transfer station to perform useful work. In accordance with this invention, the fluid is air that is stored in an enclosure (herein disclosed as a building attic) and is heated by sun rays passing through a light pervious portion of the roof of the enclosure. A light reflective surface may be so positioned on the floor of the enclosure as to reflect the sun rays into a portion of the enclosure that has a roof that is light impervious where the solar heated air is stored and from which it is transmitted, as needed, to the heat transfer station. This invention thereby provides an effective and economical system, utilizing solar energy, for effecting the transmittal of conditioned fluid to the heat transfer station.